Liquid crystal displays with relatively low operating power are in widespread use not only in mobile devices but also in stationary types. In comparison to the CRT (Cathode-Ray Tube) and the like, the liquid crystal display is slow to respond and may fail to completely respond within a rewrite time (16.7 msec) which corresponds to a typical frame frequency (60 Hz) depending on grayscale level. The issue is addressed in, for example, Japanese published unexamined patent application 2002-116743 (Tokukai 2002-116743; published Apr. 19, 2002) by driving the LCD (Liquid Crystal Display) with a drive signal modulated for a quick transition from a current to a desired grayscale level.
For example, supposing that a grayscale level transition from a current frame FR(k−1) to a next or desired frame FR(k) requires a “rise” drive, a voltage is applied to a pixel in such a manner to facilitate a transition from the current grayscale level to a desired grayscale level. Specifically, a voltage applied to the pixel is higher than that represented by video data D(i,j,k) for the next frame FR(k).
In the grayscale level transition, the application of the voltage increases the brightness level of the pixel more quickly and takes less time to raise it to proximity to the brightness level indicated in the video data D(i,j,k) for the next frame FR(k) than the faithful application of an exact voltage represented by the video data D(i,j,k) for the next frame FR(k). Thus, the liquid crystal display will have an improved response speed despite the use of slow-responding liquid crystal.
In conventional arrangements, however, noise in a video signal may enhance a grayscale level transition and produce an undesirable video output. Meanwhile, if grayscale level transition facilitation is restrained to prevent display quality from being degraded due to the noise, the response speed of the pixel may slow down.